* #set(Object)}.
   */
  private static final class CatchingFuture<V extends @Nullable Object, X extends Throwable>
      extends AbstractCatchingFuture<V, X, Function<? super X, ? extends V>, V> {
    CatchingFuture(
        ListenableFuture<? extends V> input,
        Class<X> exceptionType,
        Function<? super X, ? extends V> fallback) {

      extends AbstractTransformFuture<I, O, Function<? super I, ? extends O>, O> {
    TransformFuture(
        ListenableFuture<? extends I> inputFuture, Function<? super I, ? extends O> function) {
      super(inputFuture, function);
    }

    @Override
    @ParametricNullness
    O doTransform(Function<? super I, ? extends O> function, @ParametricNullness I input) {
      return function.apply(input);
    }

    @Override

 * @param <OutputT> the type of the output (i.e. this) future
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault
@SuppressWarnings(
    // Whenever both tests are cheap and functional, it's faster to use &, | instead of &&, ||
    "ShortCircuitBoolean")
abstract class AggregateFuture<InputT extends @Nullable Object, OutputT extends @Nullable Object>
    extends AggregateFutureState<OutputT> {

As dependencies will also be called by **FastAPI** (the same as your *path operation functions*), the same rules apply while defining your functions.

You can use `async def` or normal `def`.

And you can declare dependencies with `async def` inside of normal `def` *path operation functions*, or `def` dependencies inside of `async def` *path operation functions*, etc.

It doesn't matter. **FastAPI** will know what to do.

/// note

import static com.google.common.collect.Maps.transformValues;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import java.util.Map;

/**
 * Tests for {@link Maps#transformValues(Map, Function)}.
 *
 * @author Isaac Shum
 */
@GwtCompatible
@ElementTypesAreNonnullByDefault

You can define event handlers (functions) that need to be executed before the application starts up, or when the application is shutting down.

These functions can be declared with `async def` or normal `def`.

### `startup` event

To add a function that should be run before the application starts, declare it with the event `"startup"`:

   * generated by applying the specified functions. If multiple inputs are mapped to the same row
   * and column pair, they will be combined with the specified merging function in encounter order.
   *
   * <p>The returned {@code Collector} will throw a {@code NullPointerException} at collection time
   * if the row, column, value, or merging functions return null on any input.
   *

Remember that when you import `Query`, `Path`, and others from `fastapi`, those are actually functions that return special classes.

///

/// tip

Notice how each model's attribute with a type, default value and `Field` has the same structure as a *path operation function's* parameter, with `Field` instead of `Path`, `Query` and `Body`.

///

## Add extra information

Let's look at how we can make that work.

## pytest.mark.anyio

If we want to call asynchronous functions in our tests, our test functions have to be asynchronous. AnyIO provides a neat plugin for this, that allows us to specify that some test functions are to be called asynchronously.

## HTTPX

Even if your **FastAPI** application uses normal `def` functions instead of `async def`, it is still an `async` application underneath.

import com.google.common.annotations.GwtCompatible;
import com.google.common.annotations.GwtIncompatible;
import com.google.common.annotations.J2ktIncompatible;
import com.google.common.base.Function;
import com.google.common.base.Functions;
import com.google.common.collect.Table.Cell;
import com.google.common.collect.testing.CollectionTestSuiteBuilder;
import com.google.common.collect.testing.MapInterfaceTest;